Process of making ammonium chloride



Oct. 18, 1938.l w. HlRscHKl'ND 2,133,513

PRocEss oF MAKING AMMONIUM cHLoRIDE Filed Jan. 1o, 1936 CTL PatentedOct. 18, 1938 PROCESS F MAKING AMMONIUM CHLO- IDE Wilhelm Hirschkind,Berkeley, Calif., assignor to Great Western Electro-Chemical Company, acorporation of California Application January 10, 1936, Serial No.58,528

This invention relates to the manufacture of ammonium chloride fromammonia and hydrochloric acid.

`In Patents 1,919,943 of July 25, 1933, and 1,987,572 of January 8,1935, it has been proposed to react directly ammonia and chlorine.However, this process gives rise to chloramines. In addition, theprocess must be conducted at high temperatures and, in the case of thefirst mentioned, a close pI-I control must be maintained.

In Patent 1,654,125 of December 27, 1927, Howard has disclosed themanufacture of ammonium chloride from gas liquor and hydrochloric acid.Howard characterizes the direct reaction of gaseous hydrochloric acidand ammonia on a commercial scale as being inconvenient, expensive andinvolving the utilization of too much equipment, equipment such asreflux condensers. I have found that ammonium chloride can bemanufactured directly from hydrochloric gas and ammonia gas in a verysimple manner in equipment of a simple nature which does not involve theuse of reux condensers nor which is otherwise complicated.

It is in general the object of the present invention to provide a simpleprocess for the manufacture of ammonium chloride directly from ammoniagas and hydrochloric acid gas. n

The invention includes other objects and features of advantage, some ofwhich, together with the foregoing will appear hereinafter wherein thepresent preferred manner of practicing the process of my invention willbe disclosed.

In the drawing, the single figure is a diagrammatic representation of anapparatus for carrying out the process.

The process of my invention contemplates the use of a pool of water as ameans for absorbing both the ammonia gas and the hydrochloric acid gasat the same time that the pool provides a carrier for the ammoniumchloride formed. The addition of the ammonia gas and the hydrochloricacid gas is continued until the concentration of ammonium chloride hasbuilt up to a desired value. While the process can be conducted on acontinuous basis, additional water being added to the pool to make upfor that continuously withdrawn, I have found it convenient to operateon a batch operation scheme in accordance with which the concentrationof ammonium chloride is permitted to build up in the pool until adesired value is reached when the pool is cooled and the ammoniumchloride crystallized and recovered. By utilizing this process, I amfree from the objections raised by Howard in his aforementioned patentand I possess the additional advantage over Howard that I can utilizedirectly the gaseous reactants as well as providing a process which isindependent of the capacity of the apparatus employed.

Further details of my process will become apparent upon considering thefollowing example of operation of the apparatus disclosed.

Referring to the drawing I show an open vessel 6 containing a body ofwater or mother liquor. To this body is added through line 'I ammoniagas. 'I'he aqueous pool provided by the body absorbs the ammonia gas andprovides dilution thereof. The body is continuously circulated throughline 8 by a pump 9 to the top of a reflux tower Il. Near the base ofthis tower hydrochloric acid gas is added through line I2 while anammonium chloride solution is withdrawn through line I4 into the vessel6. In operation, the ammonia gas and hydrochloric acid gas are absorbedin the continuously circulated liquor. In this respect, the aqueousfbodyprovided suffices as a medium for absorbing the two gases and providingfor their reaction as well as for withdrawal of the ammonium chlorideformed. The absorption tower provided for the hydrochloric acid gascanbe a simple reflux column provided with a plurality of baffles sothat the hydrochloric acid gas is absorbed by the .descending streamfrom line 8.

In practice I have found it desirable to operate with an acid body andthe stream of ammonium chloride returning to the vessel 6 thereforepreferably carries hydrochloric acid in solution, preferably in aconcentration of about grams per liter. This avoids loss of ammonia whenit is added through line 1.

The hydrochloric acid gas can be produced in any preferred manner as,for instance, from hydrogen and chlorine or incidental to the niter cakeor salt cake operations. I have employed with success that processdisclosed in Patent 1,485,816 of March 4, 1924, to Rosenstein whichprocess is further developed in my joint patent with Schedler, Patent1,695,552 of December 18, 1928. The hydrochloric acid gas used can bevaried between various percentages and I have used gas coming from agenerator disclosed in the aforementioned patent with as little as 65%hydrochloric acid as well as gas entirely consisting of this acid. Thehydrochloric acid gas produced by the process of the aforementionedpatent sometimes contains free chlorine, depending upon the method ofoperation of the furnaces. The process of the present invention isparticularly applicable in the han-dling of a gas containing freechlorine, for it enables the possible formation of explosive nitrogentrichloride to be entirely avoided. Thus the ammonia is absorbed in anacid medium and in a vessel open to the atmosphere, so that if anynitrogen trichloride is formed it is immediately dispelled into theatmosphere.` At the same time, the temperature of operation ispreferably kept at such a point that the nitrogen triohloride is rapidlydecomposed by hydrolysis. The process lof the present invention alsoavoids the formation of -diilicultly handled ammonium chloride fumes,the hydrochloric acid gas being separately absorbed away from any regionWhereat it can contact with gaseous ammonia.

In operation it is not usually necessary to heat the aqueous body sincethe heat of reaction usually suices to maintain the temperature. I havefound an operating temperature between '7D-95 C. suitable and I usuallyoperate at '76 C. This corresponds to a concentration of 3'7-45%ammonium chloride for the range; at 80 the concentration is 39%. Theoperation is continued until the solution in the vessel 6 is saturatedwith ammonium chloride after which the solution is removed therefrom tocrystallizers through line l5 wherein the ammonium chloride is recoveredupon cooling the saturated solution. The mother liquor can be returnedfor further use until the impurities therein build up to an undesirableupper limit.

The process herein disclosed is in commercial operation. To provide forproduction of gray ammonium chloride, a material demanded by manyammonium chloride consumers, I have found it desirable to operate withferrie chloride present, a concentration of ferrie chloride beingmaintained in the vessel 6 of about 18 grams per liter and between l0and 2O grams per liter. This material results in the ammonium chloride,when crystallized, being a gray color. It also seems to have certaindesirable eiects upon the crystal hardness and the size of crystals andoperation of the process in the presence of considerable concentrationof ferric chloride is therefore contemplated.

To secure large crystals crystallization is conducted under quiescentconditions, usually on holders dipping in the solution. Small crystalsare secure-d in conjunction with agitation as by circulating the liquoror by air agitation.

I claim:

1. A process for producing ammonium chloride comprising maintaining anaqueous body at a temperature above about 70 C. and in such environmentas to permit escape of gases from said body, circulating a stream fromsaid body and passing the same through a tower counterconcurrently to astream of gaseous HC1, returning said stream now containing about 20grams per liter of HCl to said body, and adding ammonia to said body toreact with any HC1 in excess of that required to keep said bodyappreciably acid, removing a portion of said body, and cooling tocrystallize ammonium chloride therefrom. Y

2. A process for producing ammonium chloride comprising maintaining anaqueous body exposed to the atmosphere and at a temperature above about70 C., circulating a stream from said body and adding chlorinecontaminated HC1 thereto separate from said body, returning said streamnow containing about 20 grams per liter of HCl to said body, and addingammonia to said body to react with any HC1 in excess of that required tokeep said body appreciably acid.

3. A process for producing ammonium chloride comprising maintaining anaqueous body eX- posed to the atmosphere and at a temperature aboveabout '70 C., circulating a stream from said body and adding chlorinecontaminated HCl thereto separate from said body, returning said streamnow containing about 20 grams per liter of HC1 to said body, and addingammonia to said body to react with any HC1 in excess of that required tokeep said body appreciably acid, removing a portion of said body, andcooling to crystallize ammonium chloride therefrom.

WILHELM HIRSCHKIND.

